1. Field of the Invention
The present invention relates to a correcting method when manufacturing a cathode-ray tube. In more detail, the present invention relates to a correcting method for controlling the distance between the inner surface of the panel of a cathode-ray tube and its color selection mechanism, namely a so-called grill height, with high precision.
2. Description of the Related Art
In a color cathode-ray tube used in a television receiver, a computer display device or the like, a color selection mechanism called as an aperture grill or a shadow mask is located in an opposing relation to a color phosphor screen on an inner surface of a panel. The distance between the panel inner surface and the color selection mechanism or so-called grill height GH greatly influences the landing of an electron beam on a phosphor layer, the landing clearance between a center electron beam and side electron beams, a light intensity distribution due to diffraction phenomenon, e.g., a Fresnel diffraction of an electron beam in an electron beam passing aperture of the color selection mechanism upon forming a phosphor layer and so on. Therefore, as the color cathode-ray tube becomes more highly definite, the grill height GH is required to be high in precision.
The precision of the grill height GH is affected most by an embedding error when a panel pin, i.e., a metal pin, for supporting the color selection mechanism is embedded in the panel and an attaching error when a support spring is attached to the color selection mechanism. Up to now, for the panel pin embedding error, there is established a technique, referred to a marige spring welding method, which corrects the embedding error upon welding the support spring. However, according to this method, it is difficult to suppress the precision of grill height to less than .+-.0.15 mm and hence there is a limit to make the color phosphor screen, the color selection mechanism or the like with a fine pitch.
Also, as to the grill height GH correction, in the prior art there was no means to correct the grill height GH after the panel and the color selection mechanism were completed.